Десмонд Бэгли - Landslide

I thought so, too, but I said, ‘I wouldn’t worry too much about that, Clarry, I can handle him.’

When we pulled up in front of Mac’s cabin, Clarry said, ‘Say, isn’t that Miss Trinavant’s station wagon?’

‘It is,’ said Mac. ‘And there she is.’

Clare waved as she came to meet us. ‘I felt restless,’ she said. ‘I came over to find out what’s going on.’

‘Glad to have you,’ said Mac. He grinned at me. ‘You’ll have to sleep out in the woods again.’

Clarry said, ‘Your auto going all right, Miss Trinavant?’

‘Perfectly,’ she assured him.

‘That’s great. Well, Mr Boyd, I’ll be getting along home — my wife will be wondering where I am. Will you need me again?’

‘I might,’ I said. ‘Look, Clarry; Howard Matterson saw you with me. Will that make trouble for you? I’m not too popular right now.’

‘No trouble as far as I’m concerned — he’s been trying to put me out of business for years and he ain’t done it yet. You want me, you call on me, Mr Boyd.’ He shook his head. ‘But I sure wish I knew what was going on.’

Mac said, ‘You will, Clarry. As soon as we know ourselves.’

Summerskill went home and Mac shepherded Clare and me into the cabin.

‘Bob’s being awfully mysterious about something,’ he said. ‘He’s got some crack-brained idea that the dam is going to collapse. If it does, you’ll be four million dollars to the bad, Clare.’

She shot me a swift glance. ‘Are you serious?’

‘I am. I’ll be able to tell you more about it when I’ve looked at the cores I’ve got in the jeep. Let’s unload them, Mac.’

Pretty soon the table was filled with the lengths of two-inch cylindrical core. I arranged them in order and rejected those I didn’t want. The cores I selected for inspection had a faint film of moisture on the surface and felt smooth and slick, and a check on the numberings told me that they’d come up from the thirty-foot level. I separated them in three heaps and said to Clare, ‘These came from three borings I made today on the escarpment between the dam and the powerhouse.’ I stroked one of them and looked at the moisture on my finger. ‘If you had as many sticks of dynamite you couldn’t have anything more dangerous.’

Mac moved away nervously and I smiled. ‘Oh, these are all right here; it’s the stuff up at the escarpment I’m worried about. Do you know what “thixotropic” means?’

Clare shook her head and Mac frowned. ‘I should know,’ he admitted. ‘But I’m damned if I do.’

I walked over to a shelf and picked up a squeeze-tube. ‘This is the stickum I use on my hair; it’s thixotropic gel.’ I uncapped the tube and squeezed some of the contents into the palm of my hand. ‘Thixotropic means “to change by touch”. This stuff is almost solid, but when I rub it in my hands, like this, it liquefies. I brush it on to my hair — so — and each hair gets a coating of the liquid. Then I comb it and, after a while, it reverts to its near solid state, thus keeping the hair in place.’

‘Very interesting,’ said Mac. ‘Thinking of starting a beauty parlour, son?’

I made no comment. Instead I picked up one of the cores. ‘This is clay. It was laid down many thousands of years ago by the action of glaciers. The ice ground the rock to powder, and the powder was washed down rivers until it reached either the sea or a lake. I rather think that this was laid down in a fresh-water lake. I’ll show you something. Got a sharp knife, Mac?’

He gave me a carving knife and I cut two four-inch lengths from the middle of the same core. One of the lengths I put on the table standing upright. ‘I’ve prepared for this,’ I said, ‘because people won’t believe this unless they see it, and I’ll probably have to demonstrate it to Bull Matterson to get it through his thick skull. I have some weights here. How many pounds do you suppose that cylinder of clay can support?’

‘I wouldn’t know,’ said Mac. ‘I suppose you are getting at something.’

I said, ‘The cross-section is a bit over three square inches.’ I put a ten-pound weight on the cylinder and quickly added another. ‘Twenty pounds.’ A five-pound weight went on top of that. ‘Twenty-five pounds.’ I added more weights, building up a tower supported by the cylinder of clay. ‘Those are all the weights I have — twenty-nine pounds. So far we’ve proved that this clay will support a weight of about fifteen hundred pounds a square foot. Actually, it’s much stronger.’

‘So what?’ said Mac. ‘You’ve proved it’s strong. Where has it got you?’

‘Is it strong?’ I asked softly. ‘Give me a jug and a kitchen spoon.’

He grumbled a bit about conjuring tricks, but did what I asked. I winked at Clare and picked up the other clay cylinder. ‘Ladies and gentlemen, I assure you there is nothing up my sleeve but my arm.’ I put the clay into the jug and stirred vigorously as though I were mixing cake dough. Mac looked at me unimpressed, but Clare was thoughtful.

I said, ‘This is the meaning of thixotropic,’ and poured the contents of the jug on to the table. A stream of thin mud splashed out and flowed in a widening pool of liquidity. It reached the edge of the table and started to drip on to the floor.

Mac let out a yelp. ‘Where did the water come from? You had water already in that jug,’ he accused.

‘You know I didn’t. You gave me the jug yourself.’ I pointed at the dark pool. ‘How much weight will that support, Mac?’

He looked dumbfounded. Clare stretched out her hand and dipped a finger into the mud. ‘But where did the water come from, Bob?’

‘It was already in the clay.’ I pointed at the other cylinder still supporting its tower of weights. ‘This stuff is fifty per cent water.’

‘I still don’t believe it,’ said Mac flatly. ‘Even though I’ve seen it.’

‘I’ll do it again if you like,’ I offered.

He flapped his hand. ‘Don’t bother. Just tell me how this clay can hold water like a sponge.’

‘Remember when you looked through the microscope — you saw a lot of little flat chips of rock?’ He nodded. ‘Those chips are very small, each about five-hundredths of a millimetre, but there are millions of them in a cubic inch. And — this is the point — they’re stacked up like a house of cards. Have you ever built up a house of cards, Clare?’

She smiled. ‘I’ve tried, but it’s never got very high. Uncle John was an expert at it.’

I said, ‘Then you know that a house of cards structure is mostly empty space.’ I tapped a core. ‘Those spaces are where the water is held.’

Mac still looked a little bewildered, but he said, ‘Sounds feasible.’

Clare said quietly, ‘There’s more, isn’t there? You haven’t shown us this just as a party trick.’

‘No, I haven’t,’ I said. ‘As I said, when this sediment was first laid down it was at the bottom of the sea or a lake. Any salts in the water tend to have an electrolytic action — they act as a kind of glue to stick the whole structure together. If, however, the salts leach out, or if there were very few salts in the first place, as would happen if the deposit were laid down in fresh water, then the glueing effect becomes less. Clare, what is the most characteristic thing about a house of cards?’

‘It falls down easily.’

‘Right! It’s a very unstable structure. I’d like to tell you a couple of stories to illustrate why this stuff is called quick clay. Deposits of quick clay are found wherever there has been much glaciation — mainly in Russia, Scandinavia and Canada. A few years ago, round about the middle fifties, something happened in Nicolet, Quebec. The rug was jerked from under the town. There was a slide which took away a school, a garage, quite a few houses and a bulldozer. The school wound up jammed in a bridge over the river and caught fire. A hole was left six hundred feet long, four hundred feet wide and thirty feet deep.’